For example, Patent Literature 1 listed below describes one of hybrid electric vehicles including a motor generator, as another power source, other than an engine. In the hybrid electric vehicle disclosed in this Patent Literature 1, if operating conditions, such as, a travelling speed, are fulfilled, driving the vehicle only by the motor generator, with the engine halted, improves fuel efficiency. Patent Literatures 2 and 3 listed below describe hybrid electric vehicles including two motor generators as other power sources than an engine, in which such motor generators are controlled in response to operating conditions.
However, as Patent Literature 4 listed below describes, the vehicle vibration takes place due to cogging torque of the motor generators in motor drive mode at such extremely low speeds that the vehicle is about to come to a standstill. This is addressed by technologies, as described in said Patent Literature 3, to restrain and prevent such vehicle vibrations taking place due to cogging torque of the motor generators by controlling operations of the two motor generators. Moreover, the hybrid electric vehicles have a power split and composition device in the form of, for example, planetary gear sets, which provides a torque split or a torque composition among the torque from the engine, the motor torque from the motor generators and the reaction torque from the road.